1. Field of the Invention
The present invention relates to an optical writing device used in an image forming apparatus.
2. Description of the Related Art
There has been an increasing demand to reduce size, weight, and cost of image forming apparatuses. Color image forming apparatuses are generally larger than monochrome image forming apparatuses because the color image forming apparatuses need a lot more components than the monochrome image forming apparatuses. Therefore, there has been an increasing demand to downsize that color image forming apparatuses.
Optical writing devices (optical scanning devices) are used in image forming apparatuses. In the commercially available optical writing devices, numerous reflecting mirrors are used to reflect light beams to scan the scan targets. Because numerous mirrors are used, the optical writing device tends to be thick.
FIG. 16 is a schematic diagram of a conventional optical writing device. In this optical writing device, light beams emitted from light sources (not shown) are deflected by a polygon mirror 54, and are directed onto photosensitive elements 101 via a number of reflecting mirrors 59. Because the reflecting mirrors 59 need to be spaced apart to avoid interferences of the light beams, spacing is inevitably increased, thereby increasing the size, particularly in the up-down direction.
Japanese Patent Application Laid-open No. H4-74688 discloses an optical system for a two-color laser printer, in which a polarizing beam splitter is used to split one light beam into two sub-light beams and radiate each of the sub-light beams onto a different position on one photosensitive element.
However, Japanese Patent Application Laid-open No. H4-74688 does not disclose a technology for reducing the width of the optical writing device.